Ching Ming FestivalFestaval (if you write pinyin, write pinyin 'Qing Ming Jie', dont mix it up - at least I think so)

Today is Ching Ming Festival (清明节, qing ming jie, Tomb-Sweeping Festival), one of the 24 solar terms (二十四节气之一）. It comes on April 4th or 5th, 108 days after the Winter Solstice Solstic, which is the 22nd solar term. It is a traditional festival to honor the dead in China. On this day people go to their ancestors' grave to express our (person must agree - you used 'they') mourning and respect for the dead. It is designated as a national holiday since 2008.
Ching Ming means 'pure, clear and bright' - translated literally.  Spring arrives as comes and winter dispears departs (use related, similar verbs). It becomes warmer and warmer, trees sprouting and flowers blooming. So it is also a perfect day for touring. What a pleasure to have light and bright clothes on and hike or picnic with several friends in somewhere surounded by a sea of flowers and green vegetations (no plural form).
But unfortunately, it is gloomy today. The sun didn't show his its face even once. I preferred to(1) would rather stay at home all day rather than brave squeeze the crowd crush in the underground. The expressway is free of charge for three days 3 todays from today on, so you . You can imagine the heavy traffic on the roads, and the sequeezed terrible squeeze in the crowds in at popular interest spots those spots of interest which(3).  I experienced these last National Day, and I swear I will never again travel out on such a national holiday.

(1) 'Would rather' is conditional, but in fact you DID stay home, so use past tense.

(2) hahaha guo qing jie??? I went to Taiwan to avoid guo qing jie!  It is at first hard to see you have swapped to talking about guo qing jie.   I rearranged to sentences to reflect your meaning

(3) nowadays 'that' is preferred to 'which' except in special cases - but the changed sentence doesn't need it anyway

Ching Ming Festaval

Today is Ching Ming Festival (清明节）, or Tomb-Sweeping Festival, one of the 24 solar terms (二十四节气之一）. It comes on April 4th or 5th, 108 days after the Winter Solstic, which is the 22nd solar term. It is a traditional fesitval to honor the dead in China. On this day(,) people go to their ancestors' graves to express our (their) mourning for the dead. It is (/has been) designated as a national holiday since 2008.

Ching Ming means pure, clear and bright literally.

Ching Ming means pure, clear and bright, literally. / Ching Ming literally means pure, clear and bright.

Spring comes and winter disappears. It becomes warmer and warmer, tree sprouting and flowers blooming. So it is also a perfect day for touring. (/Therefore, it is a perfect day for touring/ It is therefore a perfect day for touring.) What a pleasure (it is) to have light and bright clothes on and hike or picnic with several friends in somewhere surrounded by a sea of flowers and green vegetations.
But unfortunately, it is gloomy today (but 好像有点多余)(and) the sun didn't (even) show his face even. I would rather stay at home all day than squeeze (into/with) the crowd in the underground. The expressway is free of charge 3 (three) todays days from today on (/onwards). You can imagine the heavy traffic on the road and the squeezed crowds in those spots of interest which (/like) I experienced last National Day. I swear I will never (again) travel out on such a national holiday.

写的好棒啊。。。

老师教过我，尽量别把阿拉伯数字参进作文除非是日期，因为不好看。